"Rebar" (concrete-reinforcing bar) end protectors are old. These plastic end protectors are used in construction sites to prevent workers from falling on the rebar ends and getting impaled or otherwise injured. A problem with existing protectors is that knocking or brushing against them easily snaps them off--dangerously re-exposing the rebar end. There are so many ways that rebar en :1 protectors get brushed off, that at any one time on a construction project, a significant number of rebar ends may be exposed and unprotected, even though workers make a conscientious effort promptly to replace dislodged protectors.